Honest advice from a long time player and short time DM is to go onto the dnd subreddits as well as just having fun. Part of the fun is learning the rules and messing up along the way. Although I'd say to start is to read through the player's handbook twice before starting. For you first session you should just plan on making your characters. Not just classes and stat, but also backstories. The first campaign you should do should probably be a prebuilt module. It's quick to use since you all just planned on starting and since you're a bit inexperienced it should be a great starting point.

Anymore advice would require a bit of context like what edition you plan on running as well as how many people will be playing.

5e, 7 players or 8

Oh boy are you going to have it rough. So new advice, find a way to keep everyone's attention. Maybe institute a no cell phone rule unless they're using it for the session, no talking when the dm opens his mouth, work hard to make the previous advice stick cause it's gonna be rough, have food available (not because it's a large group, I just forgot to mention it earlier), get a battle map and something to mark players and enemies (a group your size CANNOT do theater of the mind)

I figured as much. Thanks.